The present invention relates to apparatus for manipulating a length of flexible material (i.e. limp articles) and is particularly, but not exclusively, applicable to manipulating hose blanks.
If a length of flexible material is to be processed by an automatic machine it is necessary to first load the material appropriately prior to processing. In the case of pantyhose manufacture, for example, the processing of hose blanks to make pantyhose generally involves three basic machines namely a line closer, a toe closer and a gusset sewing machine. Linking machines are available which can automatically transfer partially processed pantyhose between one machine and the other but in order to obtain a fully automated system it is necessary that the first machine in the sequence is also loaded automatically rather than manually by an operator.
In order to effect such automatic loading it is necessary to retrieve a single length of the flexible material, in this particular example a hose blank, from a collection of them.
Most hosiery leg blanks are produced on small diameter knitting machines and after knitting each is sucked pneumatically into a dispensing device which is usually a feature of the knitting machine. The hose blanks are then ejected or dispensed from the dispensing device into a sack where they can be subject to some form of relaxation. Relaxation is a process where the hose blanks are tumbled or vibrated while being subjected to steam or hot air which has the effect of relaxing or xe2x80x9cshrinkingxe2x80x9d them. At the end of the knitting process, therefore, the manufacturer has a number of hosiery leg blanks in bags which are then delivered to the making up room to be processed by the pantyhose processing machines.
EP-A-0 737 769 discloses an apparatus for retrieving lengths of flexible material.
This application discloses a removing means for removing one or more of said lengths of material from a storage bin and arranged to release them at the entrance of a conduit, propelling means for selectively sucking and blowing the lengths of material along the conduit to or from an elongate dispenser, the dispenser having a latch means at the end nearer the propelling means and being configured so that only one of the lengths of material con be latched by the latch means and sufficiently long to hold the length of material when positioned lengthwise within it. The dispenser can be a commercially available Detexomat dispenser.
When suction is applied to the conduit the one or more lengths of material released at the entrance of the conduit are sucked to the elongate dispenser where they bunch up at a grill at the dispenser end. The latch means is then latched and by virtue of its design will engage one only, in general, of the lengths of material in the dispenser. This can be achieved by placing the latch at the apex of a narrow trapping end of the dispenser, for example, where only one of the lengths of material can reach at a time. Usually the end of the length of material will be in a position to be latched but it can happen that a folded length may be gripped at a position not adjacent an end.
The fluid flow is then reversed to act to blow the lengths of material out of the dispenser along the conduit back towards the storage bin, for example, containing the collection of lengths of material from which they came.
Only the latched length of material will remain in the dispenser, the remainder, if there was more than one in the dispenser, being returned to the collection of lengths of material. This one, latched, length of the material will generally be straightened to extend along the dispenser during this process.
The blowing is stopped after a predetermined period of time, sufficient to allow any extra lengths of material to return to the collection of lengths of material, whereupon the latch is released and the dispenser opened to allow the single length of hose to drop free of the dispenser.
This apparatus therefore allows a single length of material to be retrieved from the collection of lengths of material even if the removing means element of the apparatus is not sufficiently selective to ensure only one length of material is picked up by it.
It should be noted that the retrieval apparatus is configured so that as far as possible only one length of material is latchable, but it may be that on a rare occasion more than one may be latched, if for example two lengths are stuck together for some reason.
Generally, an end of the flexible material will be latched and so be extended along the dispenser. If not achieved it is preferable to reload the dispenser without letting the length of material already in the dispenser drop out. This can be achieved by providing means for determining the presence of the length of material a predetermined distance from the latch, e.g. by a photodetector arrangement, e.g. a SYNATEL PE2OF photodetector.
If no material is detected, the latch can be released but instead of opening the dispenser the propelling means is caused to blow again, blowing the length of material back to the collection of lengths of material.
Should no length of material have been presented to the conduit means, this determination will again show no material present at the determining means. The blowing back is now unnecessary but it can be arranged that the apparatus does so any way so the same control procedure can be used to properly locate a length of material in the dispenser just as if a folded length, say, had been latched. The single length of material dropped from the dispenser.
The apparatus of EP-A-0 737 769 includes a conveyor means positioned beneath the dispenser arranged to move the dropped length of material laterally from beneath the dispenser.
It has been found that this method of using the dispenser to orient a length of hose is generally acceptable but does, on occasion, fail to operate as designed.
Sometimes the yarn in the hose will become unravelled and become attached to grill of the dispenser used to trap the hose within the dispenser when it is sucked into the dispenser. The hose does not then fall freely from the dispenser when it is opened as it is caught at one end.
Static electricity on the nylon hose can also act to prevent the hose dropping cleanly from the dispenser and affect the way the article falls and lies on the conveyor.
Further, the hose, even if dropped cleanly, can become disoriented due to random falling action, especially by air currents and draughts that can influence the very light fabric of a hosiery article.
The present invention seeks to alleviate these disadvantages by providing an apparatus and method characterised by the features of the characterising portion of claims 1 and 5, respectively.
This apparatus provides that the article can be retrieved from the dispenser in a uniform manner.
A further advantage of the present invention is that picking the hose directly from the dispenser eliminates the stage of dropping the hose from the dispenser on to a conveyor or chute and then picking it up from a random position. That is, it eliminates the need to dispense the hose and re-pick it which is time consuming.
The gripping means may comprise a pair of spaced apart grippers but in some cases it may be necessary only to provide only one gripper. By the term gripper is meant any device which can be securely attached to the article.
If two or more grippers are present they may be independently movable or, preferably, may be mounted on a common support. This provides that the grippers can be moved by a common transport mechanism coupled to the common support, e.g. by a pneumatic or hydraulic piston/cylinder arrangement.
In a preferred embodiment of the present invention the gripping means includes one gripper and suction tube, which arrangement can provide several advantages over the dual-gripper embodiment.
Should, for any reason, two articles be retained by the dispenser, the suction tube on application of suction will suck the loose article away from the dispenser. It could conveniently be arranged that the loose article is thereby transported back to a store of the flexible materials to be picked up again at a later time.
If there is one article retained in the dispenser but for any reason the gripper fails to grip the article, again the suction tube will effect removal of the article from the dispenser, preferably to a store again to be picked up for processing at a later time.
If a single article has been retained in the dispenser and properly gripped by the gripper, the article will be held at one end by the gripper with the free length held by the suction tube with an end section of the article retained within the suction tube. This means the gripper assembly need only be able to lift that part of the hose hanging free from the gripper above the dispenser (which will be a predetermined length fixed by the distance of the gripper from the closer end of the dispenser when the article is gripped). This is because any variation in article length, due to different articles being processed, for example, will be accommodated within the suction tube with none hanging below the end of the article at the gripper. This therefore provides a gripper means with support means which need only lift the predetermined length of article from the dispenser whereupon the dispenser can be closed.
A further advantage of the gripper/suction tube arrangement is obtained when the end of the hose of the gripper is presented to a further suction tube for transporting for further manipulation or processing. On turning off the suction at the suction tube of the gripping means the article will flow easily from the suction tube to the further suction tube providing a smoother transfer of the article from the gripping means to the further suction tube than the two gripper arrangement.
The suction tube and gripper means are preferably mounted on a common support means for but mounting on distinct supports independent actuation is possible.